But neither President Obama nor Mitt Romney has offered a comprehensive plan for how he wants to overhaul the tax code.

Instead they've each made broad statements about what tax reform can achieve. And many of the tax proposals they have offered would work within the current structure of the code.

Obama stresses tax reform as way to achieve greater fairness.

"What drags our entire economy down is when ... the gap between those at the very, very top and everybody else keeps growing wider and wider," Obama said in April while making a case for his proposed Buffett Rule.

But they promise to pay for those lower rates by reducing tax breaks, primarily on the wealthy, even though there isn't enough revenue to be had by solely targeting that small slice of the population.

Stay tuned for more details from Obama and Romney -- hopefully. Until then, here's a rundown on each candidate's key tax proposals so far.

Individual income tax rates: They are currently 10%, 15%, 25%, 33%, and 35%, having been set as part of the broader Bush tax cuts. Those rates are scheduled to expire at the end of the year.

Obama: Would make the Bush tax cuts permanent for everyone except those making more than $200,000 ($250,000 if married). For those high-income households, Obama would preserve the Bush tax rates at the low end (10%, 15% and 25%) but raise the top two rates to 36% and 39.6%.

Romney: Would reduce the current Bush-era rates by 20% apiece. So the top rate would fall to 28% and the bottom rate would fall to 8%.

Alternative Minimum Tax: Currently, unless Congress makes special adjustments for inflation to the amount of income exempt from the AMT, the so-called wealth tax would hit tens of millions in the middle class. Making the adjustment is costly; getting rid of the AMT altogether is really costly.

Obama: Would permanently adjust the AMT for inflation.

Romney: Would abolish the AMT.

Investment income tax rates: Long-term capital gains and qualified dividends are taxed at 15%. Interest is subject to ordinary income tax rates. For those at or below the 15% income tax bracket, however, they have a 0% capital gains and dividend rate.

Obama: Would raise the capital gains rate to 20% and tax dividends at ordinary income tax rates for those making more than $200,000 ($250,000 if married).

Romney: Would maintain the current investment income tax rates, but exempt from taxation all capital gains, dividends and interest for those with adjusted gross income up to $100,000 ($200,000 for married couples).

Carried interest tax rate: Managers of private equity, venture capital and hedge funds are taxed at 15% on the portion of their compensation known as carried interest -- which represents a share of the profits from the funds they manage.

Obama: Would tax carried interest as ordinary income, meaning rates for fund managers would more than double.

Romney: Has in the past said the rate should not be raised. But during this campaign cycle, Romney's advisers have left open the possibility that he'd consider increasing the rate.

Tax breaks: Tax credits, deductions and other breaks reduce revenue by more than $1 trillion every year. To pay for lower income tax rates and reduce deficits, many of the hundreds of breaks on the books have to be eliminated or curtailed, experts say.

Obama: Has proposed limiting the value of itemized deductions and other tax breaks such as exclusions for those with adjusted gross income over $200,000. Today, most filers in that group can deduct 33% or 35% of a qualified expense. Obama would limit that to 28%.

Obama also has proposed making permanent some expanded tax breaks for the middle class, such as one for college costs.

Romney: Has failed to specify which tax breaks he'd eliminate or reduce to help pay for his proposed tax cuts. Last month, on CBS' "Face the Nation," he suggested that he would limit them for high-income filers, but offered no details.

Estate tax: Until the end of this year, estates valued at more than $5.12 million are subject to an estate tax up to a 35% top rate. Barring congressional action, the value of estates subject to the tax will fall to $1 million and be subject to a top rate of 55% next year.

Obama: Would reinstate the estate tax at 2009 levels -- meaning estates worth more than $3.5 million would be subject to the tax and face a top rate of 45%.

Romney: Would repeal the estate tax but preserve the gift tax rate at 35%.

Corporate taxes: Currently the top rate is 35%. Many people would like to lower it substantially. But even if all corporate tax breaks were eliminated, that would only pay for a 5.6 percentage point reduction, to 29.4%, the Congressional Research Service estimates.

Obama: Would lower the rate to 28% and pay for it by eliminating "dozens" of business tax breaks.

Romney: Would lower the top rate to 25% and pay for it by reducing corporate tax breaks.